Windows 8 學習筆記（二十三）–WritableBitmap的讀寫操作C++

在開發中，涉及圖片的處理經常需要用到WritableBitmap對象，這個對象可以直接作為資料來源賦值給Image控制項，但若要儲存這個對象，我們只能將其序列化儲存為一個圖片檔案，自然需要用到圖片的編解碼庫：

將WritableBitmap儲存為圖片檔案

WriteableBitmap^ wb =“您的源”；IBuffer^ buffer = wb->PixelBuffer;DataReader^ dataReader = DataReader::FromBuffer(buffer);Array<unsigned char,1>^ fileContent =ref new Array<unsigned char,1>(buffer->Length);dataReader->ReadBytes(fileContent);task<StorageFile^>(ApplicationData::Current->LocalFolder->CreateFileAsync(pathName, CreationCollisionOption::ReplaceExisting)).then([this,fileContent,wb](StorageFile^ file){  task<IRandomAccessStream^>(file->OpenAsync(FileAccessMode::ReadWrite)).then([this,fileContent,wb](IRandomAccessStream^ _stream){
task<BitmapEncoder^>(BitmapEncoder::CreateAsync(BitmapEncoder::JpegEncoderId,_stream)).then([this,fileContent,wb](BitmapEncoder^ encoder){            encoder->SetPixelData(BitmapPixelFormat::Bgra8,BitmapAlphaMode::Straight,wb->PixelWidth ,wb->PixelHeight,96,96,fileContent);    task<void>(encoder->FlushAsync()).then([=](void)                    {                      //Jpeg File Save Success!                    });                });         });});

 將圖片檔案讀取到WritableBitmap對象

task<StorageFile^>  ReadTask(ApplicationData::Current->LocalFolder->GetFileAsync(filename));ReadTask.then([=](StorageFile^ sampleFile){task<IRandomAccessStream^>(sampleFile->OpenAsync(FileAccessMode::Read)).then([=](IRandomAccessStream^ readStream){      int nWidth = 163;      int nHeigh = 202;      WriteableBitmap^ bitmapSnap = ref new WriteableBitmap(nWidth,nHeigh);      readStream->Seek(0);     bitmapSnap->SetSource(readStream);});});